Device for delivering fixed quantity of liquid

ABSTRACT

To deliver a liquid at high speed and with high accuracy. A device for delivering a fixed quantity of liquid, comprising a pump section for metering the delivered liquid to provide a desired amount consisting of a plunger chamber formed in a cylinder block, and a plunger reciprocating in the plunger chamber, a valve section for switching between liquid flow channels for suction and delivery, a reservoir section for reserving liquid adapted to communicate with the pump section depending upon the position of the valve section, and a delivery section having a delivery port for delivering liquid, the device being characterized in that the pump section and the valve section are disposed connected to each other and that the maximum advance position of the plunger is defined by a plane where the front end surface of the plunger contacts the valve section and pump section. The valve section is removably disposed in the pump section. The plunger chamber is made of a cylindrical chamber fitted in a hole formed in the cylinder block. The valve section is in the form of a switching valve provided with a valve block having a first flow channel communicating with a reservoir vessel and a second flow channel communicating with the delivery section.

TECHNICAL FIELD

The present invention relates to a device for delivering liquids havingany level of viscosity at high speed and with high precision, theliquids ranging from low-viscous materials, e.g., water and alcohol, tohigh-consistence fluids, such as an adhesive and pasty or creamyindustrial materials.

BACKGROUND ART

Hitherto, various types of devices for delivering a fixed quantity ofliquid have been developed; for example, (1) an air type deliveringdevice in which compressed air is applied under regulated pressure to aliquid in a reservoir vessel for a predetermined time such that adesired amount of liquid is delivered through a delivery port at anozzle fore end, (2) a plunger type delivering device in which a plungeris liquid-tightly disposed with respect to a liquid in a reservoirvessel and is moved to pressurize the liquid such that a desired amountof liquid is delivered through a delivery port at a nozzle fore end, and(3) a multi-plunger pump type delivering device having a mechanism inwhich a cylinder is disposed between a reservoir vessel and a nozzle, aplurality of penetration holes are formed in the cylinder and receiveplungers in a one-to-one relation to be able to advance or retreat, andthe liquid is sucked into the cylinder from the reservoir vessel withthe retreat of the plunger and is delivered from the cylinder to thenozzle with the advance of the plunger, the plurality of plungers actingupon the liquid in sequence to pressurize the liquid such that a desiredamount of liquid is delivered through a delivery port at a nozzle foreend.

DISCLOSURE OF THE INVENTION

However, those prior-art devices cannot deliver the liquid in a shorttact time demanded at the present, while maintaining high precision andfixed quantity.

In the die-bonding process in manufacture of semiconductors, forexample, it is demanded to deliver a larger amount of liquid in ashorter time to be adapted for not only the advent of semiconductordevices having higher performance and larger sizes, but also for ahigher tack required to increase productivity. On the other hand,high-precise delivery and fine coating of the liquid are demandedcorresponding to requirements for high-quality products.

From the viewpoint of satisfying those demands, any of theabove-mentioned prior-art devices has problems given below.

In the air type delivering device of above (1), for example, airpressure is utilized as a pressure source for delivering the liquid.However, because the air pressure is highly compressible, it is verydifficult to greatly change the air pressure in a short time.Accordingly, the air type delivering device is not suitable fordelivering the liquid at a high tact.

Also, in the case requiring a high pressure to be applied to the liquid,such as when a large amount of liquid should be delivered in a shorttime and, particularly, when the liquid to be delivered is a highlyviscous liquid, an abrupt pressure change is required in the reservoirvessel. This raises a problem that there is a limit in cutting down thedelivery time and the liquid cannot be delivered at a high tact.

In the plunger type delivering device of above (2), the plungerliquid-tightly disposed in the reservoir vessel at a level near theliquid head pressurizes all of the reserved liquid and delivers it.Here, because the amount of pressurized liquid depends upon the amountof liquid remaining in the reservoir vessel, the time required forpressurizing the liquid until reaching a desired pressure becomesshorter when the amount of the remaining liquid is small and longer whenthe amount of the remaining liquid is large. Thus, the pressure changegenerated with the delivery differs depending upon the amount of liquidremaining in the reservoir vessel, and hence causes a problem ofvariations in the amount of the delivered liquid.

If the amount of the reserved liquid is set to be small in advance, thereservoir vessel must be replaced at a shorter period, which results ina problem that the work efficiency deteriorates.

In the multi-plunger pump type delivering device of above (3), aplurality of plungers are successively operated in sequence topressurize the liquid. Upon a shift of control from one plunger toanother, therefore, the liquid is pressurized by two plungers at thesame time and therefore forces applied to the liquid are not uniform.This causes a problem that a pulsation occurs in the delivered liquidand the flow speed of the delivered liquid is not uniform.

Accordingly, when that type of device is employed to coat the liquid ona workpiece for drawing a line, a variation and a distortion occur inwidth and height of the line, and a uniform coating pattern cannot beformed. This means that, when drawing a very fine pattern, it ispractically impossible to form the pattern by coating the liquid withthe device.

It is an object of the present invention to provide a delivering device,which can overcome the above-mentioned problems with techniques fordelivering a fixed amount of liquid at high speed and with highprecision, and can deliver the liquid at high speed and with highprecision.

The present invention resides in a device for delivering a fixedquantity of liquid, comprising a pump section for metering the deliveredliquid to provide a desired amount, the pump section being consisted ofa plunger chamber formed in a cylinder block and a plunger reciprocatingin the plunger chamber, a valve section for switching between liquidflow channels for suction and delivery, a reservoir section forreserving the liquid and being communicable with the pump sectiondepending upon the position of the valve section, and a delivery sectionhaving a delivery port for delivering the liquid, the device beingcharacterized in that the pump section and the valve section aredisposed in an intimately joined relation and that a maximum advanceposition of the plunger is defined by a plane where a fore end surfaceof the plunger contacts the valve section and the pump section.

The valve section is in the form of a switching valve including a valveblock provided with a first flow channel communicating with a reservoirvessel and a second flow channel communicating with the deliverysection. In this case, the present invention resides in a device fordelivering a fixed quantity of liquid, comprising a pump section formetering the delivered liquid to provide a desired amount, a valvesection for switching between liquid flow channels for suction anddelivery, a reservoir section for reserving the liquid and beingcommunicable with the pump section depending upon the position of thevalve section, and a delivery section having a delivery port fordelivering the liquid, the device being characterized in that the pumpsection is constituted by a cylinder block in which a cylinder providedwith a plunger is formed, that the valve section is in the form of aswitching valve including a valve block provided with a first flowchannel communicating with a reservoir vessel and a second flow channelcommunicating with the delivery section, and that the pump section andthe valve section are disposed in an intimately joined relation.

The switching valve is a sliding switching valve. In this case, thepresent invention resides in a device for delivering a fixed quantity ofliquid, comprising a pump section for metering the delivered liquid toprovide a desired amount, a valve section for switching between liquidflow channels for suction and delivery, a reservoir section forreserving the liquid and being communicable with the pump sectiondepending upon the position of the valve section, and a delivery sectionhaving a delivery port for delivering the liquid, the device beingcharacterized in that the pump section is constituted by a cylinderblock in which a cylinder provided with a plunger is formed, that thevalve section is in the form of a sliding switching valve including avalve block provided with a first flow channel communicating with areservoir vessel and a second flow channel communicating with thedelivery section, and that the pump section and the valve section aredisposed in an intimately joined relation.

The pump section and the valve section are disposed in an intimatelyjoined relation by arranging the cylinder block and a valve block inclose and slide contact with each other. In this case, the presentinvention resides in a device for delivering a fixed quantity of liquid,comprising a pump section for metering the delivered liquid to provide adesired amount, a valve section for switching between liquid flowchannels for suction and delivery, a reservoir section for reserving theliquid and being communicable with the pump section depending upon theposition of the valve section, and a delivery section having a deliveryport for delivering the liquid, the device being characterized in thatthe pump section is constituted by a cylinder block in which a cylinderprovided with a plunger is formed, that the valve section is in the formof a sliding switching valve, unidirectional rotary switching valve, orreciprocating rotary switching valve having a smooth sliding surface,each of the switching valves including a valve block provided with afirst flow channel communicating with a reservoir vessel and a secondflow channel communicating with the delivery section, and that the pumpsection and the valve section are disposed in an intimately joinedrelation by arranging the cylinder block and a valve block in close andslide contact with each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of Embodiment 1.

FIG. 2 is an enlarged view of principal part of Embodiment 1.

FIG. 3 is a schematic view of Embodiment 2.

BEST MODE FOR CARRYING OUT THE INVENTION

In a method of delivering a fixed quantity of liquid by sucking a liquidfrom a reservoir vessel into a plunger chamber with a retreat stroke ofa plunger and discharging the liquid from the plunger chamber to anozzle with an advance stroke of the plunger, the method is featured inthat one delivery cycle is carried out by one sucking operation and onedischarging operation of the plunger. The liquid is never pressurized bya plurality of plungers at the same time and therefore the pressingforce applied to the liquid is kept constant. Accordingly, a pulsationdoes not occur in the delivered liquid and the flow speed of thedelivered liquid is kept uniform. As a result, even in the case ofcoating the liquid on a workpiece for drawing a line, neither variationnor distortion occur in width and height of the line, and a uniformcoating pattern can be formed. Thus, a very fine pattern can be formedby coating the liquid with the device. Further, since one delivery cycleis performed by one movement stroke of the plunger, the delivered liquidis subjected to no pulsation and the liquid can be delivered at aconstant flow speed. Hence, the liquid can be uniformly and finelycoated in a desired drawing pattern with high precision.

The term “delivery” means a phenomenon that the liquid is forced to flowout through the nozzle under a pressure difference between the pressureinduced by pressurizing the liquid and the atmospheric pressure. Inorder to effectively induce the pressure difference, therefore, thevolume of liquid to be pressurized is preferably as small as possible.The necessary least volume of pressurized liquid enables the liquidpressure to quickly rise and is effective when delivering a large amountof liquid for a short time, particularly when the liquid to be deliveredis a highly viscous liquid. For that reason, it is more preferable tosuck the liquid in amount corresponding to one delivery cycle into theplunger chamber and pressurize the sucked liquid than to pressurize theliquid in amount corresponding to plural delivery cycles. Morepreferably, there is no liquid remaining in the plunger chamber afterthe plunger has ended the operation of discharging the liquid. Accordingto the present invention, since the liquid in amount delivered in onecycle is sucked into the plunger chamber and the sucked liquid in theplunger chamber is delivered under pressure applied upon movement of theplunger, the liquid to be pressurized can be minimized, and henceadverse influences caused by the excessive amount of liquid can beeffectively eliminated. Further, it is possible to greatly cut down thetime from the pressurization of the liquid to the delivery of the liquidthrough the nozzle, and to realize the delivering operation at highspeed.

Here, the liquid suction start position and the liquid discharge endposition of the plunger are preferably held the same in each deliverycycle. Keeping always constant the amount of liquid to be pressurized ineach delivery cycle results in the following advantages. The amount ofliquid to be pressurized does not depend upon the amount of liquidremaining in the reservoir vessel, and the process in increasing theliquid pressure when the plunger pressurizes the liquid for delivery canbe made identical in each delivery cycle. Hence, no variations arecaused in the amount of the delivered liquid depending upon the amountof liquid remaining in the reservoir vessel. More preferably, the liquiddelivery start position of the plunger is kept the same in each deliverycycle, and the liquid delivery end position of the plunger is kept thesame in each delivery cycle. With the liquid delivery start and endpositions of the plunger always kept the same in each delivery cycle,the degree by which the liquid is compressed can be always held constantwithout depending upon the amount of liquid reserved in the reservoirvessel, and the liquid can be stably delivered with high precision. Evenmore preferably, the liquid suction start position of the plunger iskept the same in each delivery cycle, and the liquid suction endposition of the plunger is kept the same in each delivery cycle.

As a practical construction, a device for delivering a fixed quantity ofliquid comprises a nozzle for delivering the liquid, a reservoir vesselfor reserving the liquid, a cylinder block having a cylinder chamberformed in it, a plunger advancing and retreating while contacting aninner wall of the plunger chamber, drive means for driving the plunger,and a switching valve for communicating the plunger chamber with thereservoir vessel or the nozzle. In the device thus constructed, theplunger coupled to the drive means is operated to advance and retreatwhile contacting an inner wall of the plunger chamber. Specifically, theplunger is operated to retreat by a distance corresponding to the amountof liquid to be delivered, thereby sucking the liquid from the reservoirinto the plunger chamber, and the plunger is operated to advance by thedistance corresponding to the amount of liquid to be delivered, therebydischarging the liquid from the plunger chamber to the nozzle fordelivery of the liquid through the nozzle. On that occasion, when theplunger is operated to retreat for sucking the liquid into the plungerchamber, the switching valve communicates the plunger chamber and thereservoir vessel with each other, and when the plunger is operated toadvance for discharging the liquid from the plunger chamber, theswitching valve communicates the plunger chamber and the nozzle witheach other.

By communicating the reservoir vessel and the switching valve with eachother through a liquid feed tube, a liquid reservoir section and adelivery mechanism section can be provided separately from each other,and therefore the reservoir vessel can be disposed in a place convenientfor handling. For example, when the amount of liquid remaining in thereservoir vessel becomes small, it is possible to easily carry out workof replenishing the liquid into the reservoir vessel or for replacingthe reservoir vessel itself with another one in which the liquid isfilled in advance. Further, since the amount of liquid reserved in thereservoir vessel can be set to an appropriate amount according to aschedule in consideration of the pot life of the liquid used and thequantity of work per day, the work schedule per day can be designed soas to eliminate the work of replenishing the liquid or to replenish theliquid into the reservoir vessel as required.

Moreover, by communicating the nozzle and the switching valve with eachother through a liquid feed tube, the delivery mechanism section and adelivery port can be disposed separately from each other. Therefore,since the work can be performed with the delivery mechanism sectioninstalled on a stationary part and the nozzle mounted on a moving part,e.g., a robot, it is possible to construct the moving part at very lightweight. As a result, the coating work, for example, the work of drawinga desired pattern on the surface of a workpiece by coating the liquidthereon, can be performed at very high speed.

When the liquid in the reservoir vessel is a highly viscous fluid, orwhen the liquid requires to be more quickly sucked into the plungerchamber, the delivering device preferably includes a pressurizing unitfor pressurizing the liquid in the reservoir vessel to assist thesuction force caused upon the retreat of the plunger so that the liquidin the reservoir vessel is supplied to the plunger chamber underpressure.

The switching valve can be constituted as a sliding switching valve.Preferably, the switching valve is a slide valve which includes a valveblock provided with a first flow channel communicating with thereservoir vessel and a second flow channel communicating with thenozzle, and which slides to switch over the respective flow channels forcommunication between the relevant sections. As the distance between thefirst flow channel and the second flow channel disposed adjacent to eachother is reduced, a loss time caused with the switching operation can becut down and the liquid can be delivered in a shorter tact time.

The drive means and/or the switching valve can be operated in accordancewith a signal from a control section. Preferably, in the deliveringoperation, the switching valve is controlled to communicate the plungerwith the nozzle, and the drive means is controlled to pressurize theliquid. Also, in the sucking operation, the switching valve iscontrolled to communicate the plunger with the reservoir vessel, and thedrive means is controlled to suck the liquid.

The plunger can be disposed in plural number. The provision of pluralplungers enables plural cycles of delivery to be performed by differentplungers used in turn in each delivery cycle. More specifically, byoperating another plunger to such the liquid or stopping the operationof that plunger when any one of the plural plungers performs thedelivering operation, the plunger having sucked the liquid can quicklydeliver the sucked liquid in the next delivery cycle. It is thereforepossible to effectively save the time required for sucking the liquidand to realize a shorter tact time.

Further, the drive means can be provided in the same number as that ofthe plungers.

In addition, the plungers can be controlled independently of each other.With this control, the plunger speed of the delivering operationplunger, at which one of the plungers delivers the liquid, and theplunger speed of the sucking operation plunger, at which another plungersucks the liquid into the plunger chamber, can be easily adjusted todifferent speeds from each other. This is preferable in that when one ofthe plural plungers is used to delivery the liquid, the one plunger canbe operated at a speed suitable for the delivery, and when anotherplural plunger is used to suck the liquid, it can be operated at a speedsuitable for the suction.

Moreover, the liquid delivering device of the present inventioncomprises a nozzle for delivering a liquid, a reservoir vessel forreserving the liquid, a plunger pump, drive means for driving theplunger pump, and a switching valve for communicating a plunger chamberwith the reservoir vessel or the nozzle, the device being characterizedin that a cylinder block constituting the plunger pump and a valve blockconstituting the switching valve are disposed in a close and slidecontact with each other. Stated another way, a pump section and a valvesection are disposed in an intimately joined relation, and when a foreend of the plunger is positioned on a plane where the cylinder block andthe valve block join with each other, the suction is started and thedelivery is completed. The necessary least amount of liquid can betherefore pressurized without compressing an excessive amount of liquid.As a result, the delivery of the liquid can be controlled at a highresponse and hence the liquid can be delivered at a high tact. Inaddition, since the fore end position of the plunger is always kept thesame in each delivery cycle, the liquid can be delivered with highprecision.

Thus, the operations of discharging and sucking the liquid are switchedover in cooperation of advance or retreat of the plunger as a componentof the pump section with corresponding movement of the valve block as acomponent of the valve section. More specifically, when the valve blockas a component of the valve section is located in a position where thepump section and a liquid reservoir section are communicated with eachother, the plunger is retreated to a position corresponding to theamount of liquid to be delivered, thereby causing the liquid to movefrom the reservoir vessel into the plunger chamber. Then, the plunger isadvanced to a position from which it has started to retreat, therebydelivering the liquid through a fore end of the nozzle. On thatoccasion, the position where the fore end of the plunger is located atthe time of starting the retreat and at the time of completing thedelivery is defined on a plane where the cylinder block and the valveblock join with each other.

Herein, a liquid is, though just slightly, compressive and a liquidvolume is reduced when it is pressurized. In other words, a liquid mustbe compressed in order to pressurize the liquid. Also, the larger theamount of liquid to be pressurized, the more difficult is it to increasethe liquid pressure more quickly. For example, as the amount of liquidto be pressurized increases in the liquid delivering device of thepresent invention, the moving speed of the plunger must be increased toensure the identical pressure increasing process. Conversely speaking,when the amount of liquid to be compressed is small, the liquid pressurecan be increased with a smaller amount by which the plunger is advancedand retreated. Accordingly, by setting the position where the fore endof the plunger is located at the time of starting the retreat and at thetime of completing the delivery to locate on the plane where thecylinder block and the valve block join with each other, an extra liquidis avoided from being left in the plunger chamber and the amount ofpressurized liquid can be kept at the necessary least amount.

Also, since pressure is applied to act upon the necessary least amountof liquid, the liquid is delivered through the fore end of the nozzleexactly in response to the operation of the plunger. It is thereforepossible to prevent, for example, a phenomenon that the liquid continuesto drip from the delivery port of the nozzle in spite of the plungerbeing stopped after the completion of delivery. As a result, a delay ofthe completion of delivery and liquid dripping can be eliminated whichare otherwise caused upon expansion of the compressed liquid, and thedelivery of the liquid can be controlled at a high response.

Further, by setting the liquid suction start position and the liquiddelivery end position of the plunger fore end to be always constant asdescribed above, the amount of pressurized liquid residing in an areafrom the plunger fore end to the nozzle fore end is also held constant,and so is the amount by which a pressure buffer is compressed.Consequently, the amount of liquid delivered in each cycle is stabilizedand the liquid can be delivered with high precision.

In addition, since one delivery cycle is performed by one advance strokeof one plunger, the liquid delivered through the nozzle fore end issubjected to no pulsation. Moreover, since the liquid sucked into theplunger chamber is all discharged out of the plunger chamber, there isno liquid residing near the plunger and hence the liquid residing over along time is prevented from changing its properties in the plungerchamber. Taking an adhesive as an example, it is possible to avoid atrouble that the adhesive is hardened and the plunger is seized.

Operation

The operations of discharging and sucking the liquid are switched overin cooperation of advance or retreat of the plunger as a component ofthe pump section with corresponding movement of the valve block as acomponent of the valve section. More specifically, when the valve blockis located in a position where the pump section and the liquid reservoirsection are communicated with each other, the plunger is retreated to aposition corresponding to the amount of liquid to be delivered, therebysucking the liquid from the reservoir vessel into the plunger chamber inthe amount to be delivered. Then, after moving the valve block to aposition where the pump section and the nozzle section are communicatedwith each other, the plunger is advanced to a position from which it hasstarted to retreat, thereby delivering the liquid through the fore endof the nozzle. On that occasion, the position where the fore end of theplunger is located at the time of starting the retreat and at the timeof completing the delivery is defined on a plane where the cylinderblock and the valve block join with each other.

Thus, by setting the position where the fore end of the plunger islocated at the time of starting the retreat and at the time ofcompleting the delivery to locate on the plane where the cylinder blockand the valve block join with each other, an extra liquid is avoidedfrom being left in the plunger chamber and the amount of pressurizedliquid can be kept at the necessary least amount.

Also, since pressure is applied to act upon the necessary least amountof liquid, the liquid is delivered through the fore end of the nozzleexactly in response to the operation of the plunger. It is thereforepossible to prevent, for example, a phenomenon that the liquid continuesto drip from the delivery port of the nozzle in spite of the plungerbeing stopped after the completion of delivery. As a result, a delay ofthe completion of delivery and liquid dripping can be eliminated whichare otherwise caused upon expansion of the compressed liquid, and thedelivery of the liquid can be controlled at a high response.

Further, by setting the liquid suction start position and the liquiddelivery end position of the plunger fore end to be always constant asdescribed above, the amount of pressurized liquid residing in an areafrom the plunger fore end to the nozzle fore end is also held constant,and so is the amount by which a pressure buffer is compressed is furtherheld constant. Consequently, the amount of liquid delivered in eachcycle is stabilized and the liquid can be delivered with high precision.

In addition, since one delivery cycle is performed by one advance strokeof one plunger, the liquid delivered through the nozzle fore end issubjected to no pulsation.

Moreover, since the liquid sucked into the plunger chamber is alldischarged out of the plunger chamber, there is no liquid residing nearthe plunger and hence the liquid residing over a long time is preventedfrom changing its properties in the plunger chamber. Taking an adhesiveas an example, it is possible to avoid a trouble that the adhesive ishardened and the plunger is seized in the plunger chamber.

As mentioned above, the pump section and the valve section are disposedin an intimately joined relation, and when the fore end of the plungeris positioned on the plane where the cylinder block and the valve blockjoin with each other, the suction is started and the delivery iscompleted. Therefore, the necessary least amount of liquid can bepressurized without compressing an excessive amount of liquid. As aresult, the delivery of the liquid can be controlled at a high responseand hence the liquid can be delivered at a high tact.

Further, since the fore end position of the plunger is always kept thesame in each delivery cycle, the liquid can be delivered with highprecision.

It is needless to say that, in the present invention, the control meanscan perform the suckback operation by adjusting the stop position of theplunger.

Details of the present invention will be described in connection withembodiments. It is to be noted that the present invention is in no waylimited by the embodiments described below.

Embodiment 1

One embodiment of the present invention will be described with referenceto FIGS. 1 and 2.

In the Figures, numeral 31 denotes a cylinder block which is made of ablock-shaped metal material and has cylindrical penetration holes boredin it to form a plunger chamber A 31 a and a plunger chamber B 31 b. Aplunger rod A 27 and a plunger rod B 27 are fitted respectively in theplunger chamber A 31 a and the plunger chamber B 31 b to be able toadvance and retreat therein. The stroke of each plunger rod is set suchthat a front end surface of the plunger rod in its maximum advanceposition is flush with one side surface of the cylinder block 31. Avalve block 34 is disposed in close and slide contact with one sidesurface of the cylinder block 31 at which the penetration holes formedin the cylinder block 31 are opened. The valve block 34 is also held inpressure contact with the cylinder block 31 by a pushing member 35 sothat a liquid is prevented from leaking through the interface betweenboth the blocks.

Additionally, numerals 29, 30 in FIG. 2 denote seals for preventingleakage of the liquid through contact surfaces between the cylinderblock and the plunger rod.

Flow channels are formed in the valve block 34, as shown, to constitutea slide valve in cooperation with the cylinder block 31. The slide valveopens and closes flow channels between a reservoir vessel 1 and a nozzle2 to control the liquid supplied to the nozzle 2. Also, a portion of asurface of the valve block 34 held in pressure contact with the cylinderblock 31, in which the flow channels are not opened, functions as acylinder head. More specifically, the slide valve is constituted by boththe valve block 34 and the cylinder block 31. Then, the valve block 34slides relative to the cylinder block 31 to perform the flow-channelswitching operation in accordance with a signal from an air controlmeans 10 such that the plunger chamber B 31 b is communicated with thenozzle 2 when the plunger chamber A 31 a is communicated with thereservoir vessel 1, and the plunger chamber B 31 b is communicated withthe reservoir vessel 1 when the plunger chamber A 31 a is communicatedwith the nozzle 2.

Further, because the valve block 34 is held in a pressure contact statebetween the pushing member 35 and the cylinder block 31, it ispreferable for the purpose of ensuring smooth sliding of the valve block34 that contact surfaces of the valve block 34 with the pushing member35 and the cylinder block 31 each have a low coefficient of friction. Inpractice, the low coefficient of friction can be realized by reducingthe area of each of those contact surfaces.

A motor A 20 is connected to a ball screw A23 through a gear A 21.

The plunger rod A 27 is attached to a plunger-rod attachment plate A 25such that it advances and retreats with rotation of the motor A 20 whileslide-contacting with an inner surface of the plunger chamber A 31 a.

The plunger rod B 28 is attached to a plunger-rod attachment plate B 26such that it advances and retreats with rotation of the ball screw B 24while slide-contacting with an inner surface of the plunger chamber B 31b. A gear B22 coupled to the ball screw B24 is coupled to the gear A 21.With such a gear arrangement, when the plunger rod A 27 advances, theplunger rod B 28 retreats, and when the plunger rod A 27 retreats, theplunger rod B 28 advances.

The pushing member 35 is provided at a fore end of an air cylinder A 36and fixedly press the valve block 34 cylinder block in place with airpressure supplied from the air control means 10. Therefore, the valveblock 34 is brought into close contact with the cylinder block 31 andthe pushing member 35 so as to prevent useless leakage of the liquid,while allowing the valve block 34 to slide relative to the cylinderblock 31 and the pushing member 35.

By always supplying a constant air pressure force from the air controlmeans 10, the pushing member 35 provided at the fore end of the aircylinder A 36 can bring the valve block 34 into close contact with thecylinder block 31 under a desired force at all times. It is notpreferable to use a spring or the like to apply the pressing force,because the use of a spring or the like causes changes in the force forpressing the valve block 34 due to, e.g., deterioration and deformationof a spring material, etc.

Further, the use of the air cylinder A 36 is advantageous in thefollowing point. Even if the contact surfaces of the valve block 34 andthe cylinder block 31 are worn off and the effective width of the valveblock 34 is reduced, the air pressure regulated so as to provide theconstant pressing force is supplied to the air cylinder A 36, andtherefore the valve block 34 can be brought into pressure contact withthe cylinder block 31 under the force of the same magnitude as thatapplied before wearing of the contact surfaces. It is hence possible toavoid a gap being formed between the contact surfaces of the valve block34 and the cylinder block 31, and to prevent the liquid from leakinguselessly.

The air cylinder A 36 may be provided with a stopper for preventingretraction of the air cylinder A 36 and keeping the valve block 34 andthe cylinder block 31 from being separated from each other, when thevalve block 34 is subjected to a force acting to move it away from thecylinder block 31.

The valve block 34 is slidable parallel to the contact surface of thecylinder block 31 and the position of the valve block 34 is controlledsuch that the plunger chamber B 31 b is communicated with the reservoirvessel 1 when the plunger chamber A 31 a is communicated with the nozzle2, and the plunger chamber B 31 b is communicated with the nozzle 2 whenthe plunger chamber A 31 a is communicated with the reservoir vessel 1.

Such a sliding operation of the valve block 34 can be performed by theair control means 10 controlling an air cylinder B 37.

Two valve block support arms 33 are connected to both ends of the aircylinder B 37, and the valve block 34 is formed to have a width equal tothe distance between those two arms. The sliding operation of the valveblock 34 is performed with the valve block 34 held between the twosupport arms 33.

The valve block 34 is merely fixedly pressed against the two valve blocksupport arms 33 connected to the air cylinder B 37 and the pushingmember 35 connected to the air cylinder A 36 without being fixed to themby bonding. By cutting off the supply of pressure to the air cylinder A36 and reducing the pressing force of the pushing member 35 against thevalve block 34, therefore, the valve block 34 can be simply removed andeasily replaced with a new one when the valve block 34 is worn out.

A motor B 38 is coupled to a ball screw C 39. With rotation of the motorB 38, the relative distance between a base block 49 and a sub-block 50can be changed in the axial described of the ball screw C 39.

The motor A 20, the ball screw A 23, the ball screw B 24, the plungerrod A 27, the plunger rod B 28, the plunger-rod attachment plate A 25,and the plunger-rod attachment plate B 26 are each fixed to the baseblock 49. The plunger chamber A 31 a, the plunger chamber B 31 b, thecylinder block 31, the nozzle 2, and the valve block 34 are each fixedto the sub-block 50. By changing the relative distance between the baseblock 49 and the sub-block 50 with rotation of the ball screw C 39,therefore, the relative distances from the plunger rod A 27 and theplunger rod B 28 to the valve block 34 can be adjusted while therelative distance between the plunger rod A 27 and the plunger rod B 28is kept constant. Accordingly, when each of the plunger rods is justslightly displaced, for example, in the case of delivering a smallamount of liquid, the plunger rod position can be set closer to thevalve block 34. It is hence possible to effectively avoid the liquidfrom remaining uselessly.

Assuming that the middle of a maximum stroke through which each plungerrod advances and retreats is defined as a position where a fore end ofthe plunger rod A 27 and a fore end of the plunger rod B 28 are alignedwith each other, when the liquid is delivered in such an amount as notrequiring movement of the plunger rod through the maximum stroke, forexample, in the case of delivering a small amount of liquid, the plungerrod is operated to advance and retreat just through a shorter strokethan the maximum stroke. On that occasion, the liquid remaining betweenthe fore end position of the plunger rod and the valve block 34 at thetime of end of the delivery acts as a buffer. Accordingly, it ispreferable to eliminate the liquid acting as a buffer, in particular,when the liquid is delivered at a high tact.

The liquid can be replenished into the reservoir vessel 1 as theoccasion requires. Also, the reservoir vessel 1 may be replaced withanother one in which the liquid is filled in advance.

The air cylinder A 36 and the air cylinder B 37 are both connected tothe air control means 10 and are able to supply air as required.Further, the air control means 10, the motor A 20, and the motor B 38are connected to a control unit 11 and operated in accordance withsignals from the control unit 11.

The delivering operation is carried out as follows:

(1) The plunger rod A 27 and the plunger rod B 28 are adjusted such thattheir fore ends are located in positions (aligned positions) at equaldistances from the cylinder block. Each of those positions is called abase position.

(2) The motor A20 is driven to advance the plunger rod A 27 by a strokecorresponding to a volume that is equal to a half of the desireddelivery amount. At this time, the rotation of the motor A20 istransmitted to the gear B 22 through the gear A21, thus causing theplunger rod B 28 to retreat by a stroke corresponding to the volume thatis equal to a half of the desired delivery amount.

(3) The advance amount of the plunger rod A 27 from the base position inthe above state is a maximum stroke when the desired amount of liquid isdelivered. Hence, the motor B 38 is driven to move the fore end positionof the plunger rod A 27 closer to the valve block 34, whereby therelative distance between the base block 49 and the sub-block 50 isadjusted so that the amount of liquid remaining in the plunger chamber A31 a is minimized, preferably, becomes zero.

Because the plunger rod A 27 and the plunger rod B 28 are translated inunion with each other with driving of the motor B 38, the relativedistance between the plunger rod A 27 and the plunger rod B 28 remainthe same.

(4) At this point, the position of the valve block 34 is adjusted tocommunicate the reservoir vessel 1 and the plunger chamber A 31 a witheach other, i.e., to communicate the nozzle 2 and the plunger chamber B31 b with each other.

(5) Then, the motor A 20 is driven to advance the plunger rod B 28 by astroke corresponding to the desired volume of delivered liquid. At thesame time, with the rotation of the motor A 20, the plunger rod A 27retreats by a stroke corresponding to the desired volume of deliveredliquid, whereupon the liquid in the reservoir vessel 1 is sucked intothe plunger chamber A 31 a.

(6) Furthermore, the position of the valve block 34 is adjusted tocommunicate the reservoir vessel 1 and the plunger chamber B 31 b witheach other, i.e., to communicate the nozzle 2 and the plunger chamber A31 a with each other.

(7) The motor A 20 is driven to advance the plunger rod A 27 by a strokecorresponding to the desired volume of delivered liquid. Since thedesired amount of liquid is already filled in the plunger chamber A 31a, the liquid is delivered through a delivery port at the fore end ofthe nozzle 2 with the driving of the motor A 20. Also, since thereservoir vessel 1 and the plunger chamber B 31 b are communicated witheach other and the plunger rod B 28 retreats by a stroke correspondingto the desired volume of delivered liquid with the rotation of the motorA 20 at the same time, the liquid in the reservoir vessel 1 is suckedinto the plunger chamber B 31 b.

(8) Subsequently, the liquid is successively delivered by repeating theoperations of above 4 to 7.

Thus, at the same time when the liquid is delivered upon advance of oneof the plunger rods, the other plunger rod sucks the liquid into thecorresponding plunger chamber. As a result, the delivering operation canbe performed at a high tact.

Embodiment 2

In above Embodiment 1, two plunger rods are driven by one motor. In thisembodiment, however, two motors 60, 61 are connected respectively to twoplunger rods 27, 28, and an air pressure is applied to the liquid in thereservoir vessel 1 so that the liquid can be quickly filled into theplunger chambers A 31 a, B 31 b from the reservoir vessel 1. Mainfeatures of this embodiment are as follows.

(1) The motors 60, 61 are connected respectively to two ball screws 23,24, and therefore the two plunger rods 27, 28 can be moved independentlyof each other. This arrangement enables the speeds of delivery andsuction to be changed as required. For a liquid requiring a longer timeto suck it, therefore, the filling speed can be reduced without changingthe delivery speed, and the occurrence of cavitation can be suppressedwithout causing an inadequate suction force to act upon the liquid.

(2) By rotating the two independent motors 60, 61 in the same direction,the relative distances from the plunger rod A 27 and the plunger rod B28 to the valve block 34 can be adjusted while the relative distancebetween the plunger rod A 27 and the plunger rod B 28 is kept constant.In Embodiment 2, therefore, it is no longer required to provide the baseblock and the sub-block separately from each other and to slide thesub-block by the motor, as shown in FIG. 3.

(3) The air control means 10 is able to pressurize air in the reservoirvessel 1 so that the liquid can be quickly sucked into the plungerchambers A 31 a, B 31 b from the reservoir vessel 1. Accordingly, theliquid can be supplied to the plunger chambers at higher speed and thedelivering operation can be performed at a shorter tact time. Thisfeature is particularly much effective in the case of delivering ahighly viscous liquid. In the present invention, the reservoir vesseland the cylinder block may be communicated with each other through aliquid feed tube. With such a modification, the reservoir vessel can beinstalled in a position remote from the device body, and hence thereservoir vessel can be easily replaced with a new one even when thedevice body is installed in apposition beyond the range easilyaccessible by a worker. Likewise, the valve block and the nozzle may becommunicated with each other through a liquid feed tube.

Embodiment 3

While above Embodiments 1 and 2 employ, as the switching valve, asliding switching valve, this embodiment employs, as the switchingvalve, a rotary switching valve having a smooth sliding surface. Morespecifically, a disk-like valve body having an arc-shaped flow channelformed in its surface held in contact with the cylinder block is rotatedin one direction or reciprocally. Under cooperation of the arc-shapedflow channel formed in the disk-like valve body with a hole formed inthe surface of the cylinder block held in close contact with the valveblock and communicating with a pump section, a hole formed in that closecontact surface and communicating with the liquid reservoir vessel, anda hole formed in that close contact surface and communicating with thenozzle, the switching valve performs the switching operation between astate in which the pump section is communicated with the liquidreservoir vessel and a state in which the pump section is communicatedwith the nozzle, as in Embodiment 1 or 2.

Any of the above embodiments has been described as including two pumpsections. However, the present invention can also be constructed suchthat only one pump section is provided and the liquid flow channel isswitched over to communicate the plunger chamber and the liquidreservoir vessel with each other or to communicate the plunger chamberand the nozzle with each other.

Further, the above embodiments employ the plunger chambers directlybored in the cylinder block, but the plunger chambers can be formed byboring a fitting hole in the cylinder block and fitting a separatecylinder to the fitting hole. In addition, it is possible to use, as thecylinder block, a material that is relatively easy to machine, to formthe plunger chamber by fitting the separate cylinder to the fitting holebored in the cylinder block, and to employ a hard member to form asliding surface of the cylinder block held in close contact with thevalve section.

Additionally, even in the case in which the plunger chambers aredirectly formed in the cylinder block, the sliding surface of thecylinder block held in close contact with the valve section may beformed of a hard member because the contact surface of the cylinderblock with the valve section is heavily worn.

INDUSTRIAL APPLICABILITY

As described above, since the pump section and the valve section aredisposed in an intimately joined relation, and the maximum advanceposition of a plunger is defined by a plane where a fore end surface ofthe plunger contacts the valve section and the pump section, thenecessary least amount of liquid can be pressurized without compressingan excessive amount of liquid. Accordingly, delivery of the liquid canbe controlled at a high response and hence the liquid can be deliveredat a high tact.

Further, since the fore end position of the plunger is always kept thesame in each delivery cycle, the liquid can be delivered with highprecision.

1. A device for delivering a fixed quantity of liquid, comprising a pumpsection for metering the delivered liquid to provide a desired amount,said pump section being consisted of a plunger chamber formed in acylinder block and a plunger reciprocating in said plunger chamber, avalve section for switching between liquid flow channels for suction anddelivery, a reservoir section for reserving the liquid and beingcommunicable with said pump section depending upon the position of saidvalve section, and a delivery section having a delivery port fordelivering the liquid, characterized in that said pump section and saidvalve section are disposed in an intimately joined relation, and that amaximum advance position of said plunger is defined by a plane where afore end surface of said plunger contacts said valve section and saidpump section.
 2. A device for delivering a fixed quantity of liquidaccording to claim 1, wherein said valve section is installed removablyfrom said pump section.
 3. A device for delivering a fixed quantity ofliquid according to claim 1, wherein said plunger chamber is defined bya cylindrical member fitted in a hole bored in said cylinder block.
 4. Adevice for delivering a fixed quantity of liquid according to claim 1,wherein said valve section is in the form of a switching valve includinga valve block provided with a first flow channel communicating with areservoir vessel and a second flow channel communicating with saiddelivery section.
 5. A device for delivering a fixed quantity of liquidaccording to claim 1, wherein said switching valve is a slidingswitching valve.
 6. A device for delivering a fixed quantity of liquidaccording to claim 1, wherein said switching valve is a rotary switchingvalve having a smooth sliding surface.
 7. A device for delivering afixed quantity of liquid according to claim 5, wherein said deviceincludes a slide valve brought into close contact with said cylinderblock under action of pressure.
 8. A device for delivering a fixedquantity of liquid according to claim 1, wherein said device includespressurizing means for pressurizing the liquid in a reservoir vessel. 9.A device for delivering a fixed quantity of liquid according to claim 1,wherein said device includes a plurality of pump sections, and aplurality of plungers constituting said pump sections are driven by onedrive source.
 10. A device for delivering a fixed quantity of liquidaccording to claim 1, wherein said device includes a plurality of pumpsections, and a plurality of plungers constituting said pump sectionsare driven by drive sources independent of each other.
 11. A device fordelivering a fixed quantity of liquid according to claim 6, wherein saiddevice includes a slide valve brought into close contact with saidcylinder block under action of pressure.